I’m trying to match characters that shouldn’t be allowed in a username string to then be replaced.
Anything outside this range should match first character [a-zA-Z] <– restricting the first character is causing problems and I don’t know how to fix it
And then match everything else outside this range [0-9a-zA-Z_.] <—- repeat until the end of the string
Matches:
- /////hey/// <– first match
/////, second match/// - [][123Bc_.// <– first match
[][, second match// - (/abc <– should match
(/ - a2__./) <– should match
/)
Non Matches:
- a_____
- b__…
Current regex
/^([^a-zA-Z])([^w.])*/
const regex = /^([^a-zA-Z])([^0-9a-zA-Z_.])*/; '(/abc'.replace(regex, '') // => return expected abc '/////hey///'.replace(regex, '') // => return expected "hey"
Advertisement
Answer
/^([^a-zA-Z])([^w.])*/
You can not do it this way, with negated character classes and the pattern anchored at the start. For example for your va2__./), this of course won’t match – because the first character is not in the disallowed range, so the whole expression doesn’t match.
Your allowed characters for the first position are a subset, of what you want to allow for “the rest” – so do that second part first, replace everything that does not match [0-9a-zA-Z_.] with an empty string, without anchoring the pattern at the beginning or end.
And then, in the result of that operation, replace any characters not matching [a-zA-Z] from the start. (So that second pattern does get anchored at the beginning, and you’ll want to use + as quantifier – because when you remove the first invalid character, the next one becomes the new first, and that one might still be invalid.)